What happened

It has been a sizzling year for Shake Shack (NYSE:SHAK) shareholders as the stock gained 59% in the first half of 2019 compared to a 17% increase in the S&P 500, according to data provided by S&P Global Market Intelligence.

A man takes a bite out of a burger.

Image source: Getty Images.

So what

Investors were pleased to hear that the better-burger chain ended fiscal 2018 on an upswing. Customer traffic returned in the fourth quarter, leading to comparable-store sales growth of 2% compared to a minor decrease in the prior quarter. That positive momentum continued into the new year, with comps rising nearly 4% in the first quarter thanks to a mix of higher prices and increased customer visits.

Now what

Shake Shack's core growth figures still aren't impressive compared to the wider industry. Leader McDonald's, after all, far outpaced the upstart's comps over the past year.

But investors are excited about the potential for much a larger sales base as Shake Shack expands beyond its current limited focus. That prospect seemed remote when the company was posting consistent market-share losses at existing locations, but it's more likely now that it is achieving industry-beating sales metrics.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.